Smart Process Distillation Application Improves Recovery And Saves Energy

SmartProcess Distillation Application Improves Recovery and Saves Energy – A Case Study Pete Sharpe Director, Industry Solutions for Refining & Chemicals

Presenters
Pete Sharpe

Agenda
Operating Challenges
Project Methodology
Process Overview
Process Flow
Operating Objectives
SmartProcess® Distillation Optimizer
Results

Operating Challenges
Purification unit involving multiple distillation trains with 11 columns
Ultra-high purity product specifications require very tight quality controls
Multiple large, 200+ tray columns with extremely long time constants
Large energy consumer
Different feedstock suppliers with different qualities unloaded from railcars
Safety margins required to compensate for disturbances in feed quality

Project Methodology
APC licenses were specified and included as part of the DeltaV migration project
Capital expense
Functional Specification prepared by Emerson that included the design for the complete process unit (11 distillation columns)
Initial implementation phase covered only the first column in the series
Gain customer experience with technology
Develop Operator acceptance
Demonstrate value to management
Subsequent phases to be implemented by customer engineers with support from Emerson APC Consultants

Project Implementation
FDS phase included on-site audit of instrumentation and control strategies and preliminary step tests
Identified regulatory control issues that needed to be addressed prior to on-site work
Software installation of SmartProcess application performed by customer personnel prior to on-site work
Emerson consultants spent 2 weeks on-site for configuration and commissioning
Performance improvements estimated and presented to operations management based on initial trial run

Advanced Control Solution
SmartProcess® Distillation Optimizer
Utilizes Embedded DeltaV Advanced Process Control
On-Line Key Performance Indicator (KPI) Calculations
Emerson APC Consulting Services
Functional Design
Control Performance Audit
Implementation Assistance
Initially started with first column in the train that removes light contaminates

Process Overview Bottoms Main Product Feed 1
Column separates components based on different boiling points
Tray temperatures reflect composition on that tray, but need to be compensated for pressure
Control strategies based on “What comes in must go out”
Material Balance
Energy Balance
Material Balance:
OH / Feed Ratio
Energy Balance:
Reflux / Feed Ratio
Feed 2 At constant OH rate, this temp sets the energy balance (R/F). Internal Reflux Lt Ends Impurities This flow sets the material balance (D/F) Complicated OH condenser system LC TC TI

Distillation Process Affect of Energy Lt Key Concentration Energy Consumption  Feed Composition 100% 0% Overhead Composition Bottoms Composition At Constant D/F Ratio

Cost of Variability Precision Control Valves Loop Performance Digital Positioners Better Measurements IMPROVED PROFIT BY CHANGING TARGET REDUCED VARIABILITY POOR CONTROL $ PROFIT SPECIFICATION LIMIT Improvements from: Operator Safety Margin Advanced Control

APC Optimization Time Distillate Rate Recovery Opportunity Minimum OH Rate Operator Setpoint APC Objective: Minimize overhead product loss while controlling bottoms impurities to target

SmartProcess Applications – Tools vs. Solutions We have the best materials, craft skills, tools, and services. What can we build for you? We’ve developed a variety of houses to meet your specific needs. Products, Services, Expertise Applications

What are SmartProcess Applications?
Re-usable applications that can be pre-engineered and used multiple times
Combination of:
DeltaV composite blocks, modules & templates
APC tools (e.g. PredictPro, Neural)
DeltaV Graphics
Documentation
Sample Configuration
Simple dynamic simulation

Applications Enable Faster, More Efficient APC Implementations Functional Design Det. Design, Config & Staging Step Tests & Model ID Commissioning Functional Design Det. Design & Config Step Tests & Model ID Commissioning Commissioning Step Tests & Model ID F.D. & Config Traditional APC Technology Embedded APC Technology SmartProcess ® Applications with Embedded APC

SmartProcess Distillation Control Module Standard Distillation Calcs Predict Block Preconfigured Neural Blocks Module Library

Standard Operator Display & Simulation

Manipulated Variables (MV) – Controller setpoints written to by the MPC.
Distillate Rate
Reboiler Steam
Controlled Variables (CV) - Process variables which are to be maintained at a specific value; i.e., the setpoint
Lower tray Pressure Compensated Temperature (PCT)
Overhead PCT
Disturbance Variables (DV) - Measured variables which may also affect the value of controlled variables
Feed Flows (2)
Reflux Temp
Constraints (LV) - Variables which must be maintained within an operating range (a special type of CV)
Overhead product loss (on-line analyzer)
Light impurities in bottoms (on-line analyzer)
Internal Reflux Rate
Column Delta Pressure
Reflux/Distillate Ratio
Key Process Variables

Process Issues
Reboiler steam instability
Interaction between parallel reboilers with common steam trap, one fouled, one clean. In Manual and Auto, steam flow varied ~10kLb/Hr out of 50. Process design issue.
Caused ~0.5 Deg F variability in tray temp used as CV
Overhead pressure controller range
Pressure is controlled by two valves in the condenser system, one large and one small
OH PIC operates small valve with large valve normally in Manual.
Small valve had insufficient range to control between day and night
Pressure swings caused changes in temps and qualities
Implemented control function to adjust large valve to keep small valve in control range
Small process gains
Issue primarily due to big difference in instrument ranges
Solved by using scaler blocks for process inputs

Reboiler Flow Variability Steam Condensate Drum Parallel Reboilers Tray Temps Spare Fouled Clean FC TC LC

Pressure Effects OH and Btms compositions show day-night swing due to column pressure Pressure looked fairly stable

Steam Step Tests Test Compromised due to OH pressure swings Btms Impurity OH Prod Loss Rebolier Out T OH Pressure Steam

Model Verification Btm PCT Btm Impurity OH Composition Top PCT

Initial Closed Loop Operation – Small Gains Both MV’s slowly reduced, but no observable control action

Initial Controller Results OH Prod Loss Btm Impurity OH PCT Btm PCT Steam OH Flow Step Tests APC ON

Summary of Results
Controller immediately started reducing distillate rate and OH product losses
Average OH product loss reduced by approximately 22%
Impurities in Btms were maintained within specifications.
Steam usage reduced on average around 7%
Estimated value over $700k per year

Summary
High-purity distillation columns offer significant opportunities for improvement from APC
A SmartProcess® Distillation Optimizer was implemented on a large purification column
Following the functional design, the project was completed in 2 weeks on-site
Excellent project payback achieved

Where To Get More Information
Exhibit Hall
SmartProcess Booth
Emerson Consulting Booth
DeltaV Advanced Control Booth
Contacts:
[email_address]
Website:
http://www.emersonprocess.com/solutions/consulting/advancedautomation/smartprocess.asp

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Smart Process Distillation Application Improves Recovery And Saves Energy

by Jim Cahill on Oct 28, 2009

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Smart Process Distillation Application Improves Recovery And Saves Energy — Presentation Transcript